a few months ago i was issued a ticket for driving with expired plates and the officer suggested that if i take it to court and show the registration with the new sticker they'll drop the charges. I did get the renewal sticker and am waiting for my courtdate to come in the mail

Thing is, since then i've been having numerous mechanical problems with it and i've decided to buy a new car.

So, my question is: Do i have to hang on to my old car until the court date just to show them the renewal sticker or can i show the receipt for it?

(btw, this is my first offence so you'll have to excuse my lack of knowledge in these cases)

I don't think that holding on to the care offers any more value to the prosecutor to make their decision than a receipt and/or photocopy of the ownership. However, I don't know whether they will drop it or not. I guess it depends on your region, but in my experience they don't just drop the charge if you get your plates updated. If you get your plates updated it just means you're not going to get another ticket. I think a plea with a submission for a reduced fine might be more realistic.